Bladed Gas Turbine Engine (GTE) rotors include axial compressor, radial or centrifugal compressor, axial turbine, radial-inflow turbine, and fan rotors. The thermal and mechanical demands placed on a bladed GTE rotor can vary significantly across the rotor during engine operation. Specifically, the rotor blades are typically bathed in the core gas flow during engine operation and are consequently exposed to high temperature, chemically-harsh (e.g., corrosive and oxidative) environments. In contrast, the inner “hub disk” portion of the rotor is largely shielded from the core gas flow path, but is subject to considerable mechanical stress resulting from the centrifugal forces acting on the rotor at high rotational speeds. Performance benefits can thus be realized by producing a GTE rotor having a hub disk and rotor blades fabricated from different alloys tailored to their specific operating environments. For example, an inserted blade approach can be utilized to produce a GTE rotor having a hub disk and rotor blades fabricated from different alloys. To produce such an inserted blade rotor, a number of bladed pieces are first produced from an alloy selected to provide good mechanical strength and oxidation resistance under high temperature conditions. Each bladed piece is fabricated to include at least one blade, which projects from an enlarged base portion or shank. The shanks are inserted into mating slots provided around the periphery of a separately-produced hub disk, which is fabricated from an alloy having high mechanical strength at operational temperatures. The shanks and mating slots are formed to have an interlocking geometry, such as a fir tree or dove tail interface, which prevents disengagement of the shanks in a radial direction during high speed rotation of the rotor.
While enabling the fabrication of a GTE rotor having a disk and blades fabricated from different alloys, the above-described manufacturing approach is limited in several respects. The formation of geometrically complex mating interfaces between the shanks and the hub disk often requires multiple precision machining steps, which add undesired cost, duration, and complexity to the manufacturing process. Additionally, it can be difficult to reliably form a complete seal between the mating shank-disk interfaces. If not fully sealed, these interfaces can trap debris potentially resulting in corrosion-driven failures and permit undesired leakage across the GTE rotor during engine operation. As a still further limitation, the formation of the mating shank-disk interfaces may necessitate an increase in the overall size and weight of the bladed GTE rotor to achieve a structural integrity comparable to that of a single piece or monolithic GTE rotor. Certain other manufacturing methods have been developed wherein the disk hub and blade rings are separately produced from different alloys and subsequently bonded together or metallurgically consolidated to produce a so-called “dual alloy rotor”; however, such approaches are generally restricted to the usage of equiax superalloys having inferior high temperature properties as compared to single crystal and directionally-solidified superalloys.
It is thus desirable to provide methods for manufacturing bladed GTE rotors enabling the joinder of a plurality of blades (e.g., in the form of an outer blade ring) to a hub disk in a manner that reduces the cost and complexity of manufacture, that minimizes leakage across the turbine rotor, and that allows decreases in the overall size and weight of the turbine rotor. It would also be desirable if, in at least some embodiments, the manufacturing method would enable production of the outer blade ring from a plurality of individually-fabricated bladed pieces, which could be cast or otherwise fabricated from a wide variety of high temperature materials including single crystal and directionally-solidified superalloys. Finally, it would be desirable to provide embodiments of a bladed GTE rotor produced utilizing such a manufacturing method. Other desirable features and characteristics of embodiments of the present invention will become apparent from the subsequent Detailed Description and the appended Claims, taken in conjunction with the accompanying drawings and the foregoing Background.